Newer Lithium-ion (Li-ion) chemistries for rechargeable electrochemical cells have usable voltage ranges significantly different than the conventional voltage range of approximately 3.0 to 4.2 volts. The usable voltage ranges of some newer Li-ion systems extend well below the conventional voltage range. Some battery-powered electronic devices may be able to use both conventional and newer battery cell chemistries as they can be packaged in similar housings or battery packages designed for those devices. However, conventional battery-powered electronic devices are not be designed to take full advantage of the lowest end of the usable voltage range of newer battery cell chemistries. As a result, either of two scenarios will occur which could compromise user experience when the newer-chemistry battery is at a low state of charge. In one case, when powering up the battery-powered device, the device may assert too great a load on the battery, causing battery voltage to sag below the minimum operating voltage of the electronic device. Second, the device may assert its load on the battery for too long a time, draining battery energy, resulting in low battery voltage, which drops below the minimum operating voltage of the electronic device. In both cases, the electronic device would unexpectedly shut down. This issue may be exacerbated when various device features or functions are engaged, varying the load on the battery, resulting in device shut-down when a high-current-load function is engaged.
A sophisticated battery powered device that has a varied power demand can include a power up threshold and an under-voltage threshold setting to prevent inadvertent shutdown of the battery powered device. The power up threshold is a sufficient voltage level (of the battery) at which the device can be fully functional, including high power demand functionality, to ensure there is a desirable amount of charge in the battery. The power up threshold is observed when the device is turned on, and determines that the battery voltage is below the power up threshold. Until the battery voltage rises above the power up threshold, the device will not allow full functionality, if any. Likewise, the device will begin shutting off functionality as the battery voltage is decreasing and falls below the under-voltage limit. However, these thresholds are programmed into the device, and may not apply to new battery systems that are developed subsequently to the manufacture of the device.
Accordingly, there is a need for a method and apparatus for a device to determine and use voltage limits appropriate for a variety of battery systems, including battery systems developed after the manufacture of the device.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.